Human naturally suckle by instinct, however, as teeth appear in the weaning period, they begin training to eat a solid foods little by little thereby learning mastication. Mastication is a series of actions for processing food into a state so as to enable the food to be swallowed (deglutition) as small food materials by cutting and crushing the food involving with almost all organs in the mouth such as teeth, tongue, lips, cheeks and throat. When a learning action of mastication is neglected, dental caries between teeth or a fisher caries of molar tooth, a snaggletooth, or gingivitis is liable to be caused. This mastication is similar to a state in which rice cake is pounded in a mortar. That is, a pestle and a mortar correspond to teeth and what participate in kneading are tongue, lips, and cheeks.
Further, teeth do not attach to the bone of the jaw, but a membrane (periodontal ligament) with a thickness of about 200 μm is interposed between tooth and bone of jaw and functions as a cushion, and also serves as an extremely sensitive sensor to control the masticatory movement. During mastication, a load of several tens kilograms, that is, a force of about half the body weight acts on between the upper and lower teeth. At this time, the periodontal ligament is compressed and reduced to a thickness of less than 100 μm. In this manner, direct collision of the upper and lower teeth is avoided, and sensing is performed so as to prevent the teeth from being damaged by a foreign matter such as sand. This is similar to a phenomenon that a pestle does not directly hit a mortar when rice cake is pounded.
As described above, a masticatory efficiency has very great significance for humans. Therefore, an importance has been placed on objective examination of a masticatory efficiency and accurate evaluation of the examination results as basic objects of the dental health care, and many studies have been made since a long time ago.
However, the fact is that with these study results, the accuracy has not reached such a level that the method can be applied to a stage of clinical dentistry.
On the other hand, a technique for the function of general organ, for example, a visual acuity test in the ophthalmology, and a hearing test in the otolaryngology, has been developed and adopted in the medical department since a long time ago, which has made a huge contribution to advancement from an academic view point and development of therapeutic techniques. However, the fact is that there has been almost no technique for a test of a masticatory efficiency in the dentistry.
In light of the above circumstances, the present inventors have developed and proposed “Sosyaku Kino Hyoka-yo no Kinosei Biryushi wo Ganyu suru Jinko Syokkai (Artificial food material containing functional microparticles for evaluating masticatory efficiency)” characterized by containing a lot of functional microparticles for evaluating a masticatory efficiency which have a substantially uniform spherical shape and are only squashed by an occlusion pressure and are not crushed (Japanese Patent No. 2900947).
A person with malocclusion was allowed to masticate this artificial food material, and a masticatory efficiency could be objectively and accurately evaluated. In this method, after the person is allowed to masticate 100 chewing strokes an artificial food material obtained by containing spherical microparticles which get flattened during mastication without being crushed even if they are masticated in a chewing gum base, only the microparticles are separated by removing the gum base and passed through a sieve with slit-like pores, and then, spherical microparticles and flattened microparticles are tried to be accurately measured using an electron balance.
However, in this evaluation method, problems as described below remained.
Firstly, a method for producing the microparticles to be incorporated in the artificial food material could be applied to a laboratory. However, its technique has not yet fully developed as an industrial production method and it was difficult to produce a large amount of microparticles enough to be used by each dentist.
Secondly, there was a problem that in a process of measuring a ratio of deformed microparticles after masticating, a large amount of an organic solvent such as dichloromethane was required to be used.
Thirdly, in this evaluation method, a relatively expensive equipment was needed, and further, it took a long time of 1 hour or more to perform the measurement.
Due to these reasons, although this technique is a method for evaluating a masticatory efficiency that enables sufficient evaluation using an equipment and the like which a dental research institute usually has, it was difficult to evaluate of a masticatory efficiency in a dental clinic, therefore, this technique did not spread sufficiently.
On the other hand, Ishikawa et al. have proposed chewing gum which changes its color for evaluating a masticatory ability of a person using denture J Jpn Prosthodont Sci., 46, 103-109 (2002)). This is useful for qualitative evaluation, but it is difficult to quantitatively evaluate a masticatory ability by this method.
Accordingly, an object of the invention is to provide a system for evaluating a masticatory efficiency with high accuracy in a short time without using an organic solvent and an expensive equipment for evaluation.    Patent document 1: Japanese Patent No. 2900947    Non-patent document 1: J Jpn Prosthodont Sci., 46, 103-109 (2002)